(1) Field of the Invention
The present invention pertains to a conduit connector grommet that is attachable to an opening in an enclosure wall of an electrical device to protect electrical conductors passing through the opening. In particular, the present invention is directed to a twist lock conduit connector grommet that can be attached over an opening in the enclosure wall of an electrical device without the need for separate fasteners. The twist lock grommet protects the insulation of electrical conductors passing through the opening of the enclosure wall, seals the opening from its exterior environment, and provides a connection outside the enclosure wall for the attachment of a length of conduit through which the electrical conductors are passed.
(2) Description of the Related Art
For electrical devices contained in protective metal enclosures, for example electric motors or electric generators, the insulated electrical conductors of the devices typically pass through openings provided in the metal enclosure walls of the devices. In order to protect the insulation of the conductors of such a device from being scrapped or cut by an exposed edge of the opening in the metal enclosure wall, various different types of flexible grommets have been designed. The grommets often have a general circular shape and are press fit into the opening in the enclosure wall. The electrical conductors pass through the center of the grommet with the grommet protecting the insulation of the conductors from the metal edge of the enclosure wall.
Protective grommets of the above-described type were found to be disadvantaged where the electrical device is employed in an environment where it would be exposed to moisture, dust or dirt. The center hole of the grommet would protect the insulation of the electrical conductors from the metal edge of the enclosure wall, but would often not seal closed the opening through the enclosure wall. This would permit moisture, dust and/or dirt to enter the interior of the enclosure of the electrical device where it could detrimentally affect the performance of the electrical device.
To overcome this disadvantage, grommets were designed that had exterior walls that would extend a short distance outwardly from the periphery of the grommet and overlap the enclosure wall of the electrical device around the area of the opening in the wall provided for the electrical conductors. In addition, some grommets were provided with short lengths of conduit that projected outwardly from the grommet attachment to the enclosure wall. The insulated conductors of the electrical device would extend through the grommet conduit. A separate length of conduit, for example plastic or metal tubing, would then be attached over the exterior of the grommet conduit with the electrical conductors extending through the separate length of conduit. Together, the exterior wall of the grommet, the grommet conduit and the separate length of conduit would protect the insulation of the electrical conductors as they pass through the opening in the enclosure wall of the electronic device and would also seal the interior of the electronic device from any external contaminants. Examples of these types of grommets are disclosed in the U.S. Pat. No. 5,519,273 and U.S. Pat. No. 5,777,409.
However, protective grommets of the type disclosed in the above-referenced patents are limited in their use. Grommets of this type are specifically designed to be inserted in a notch formed in an enclosure wall at an interface between an edge of the enclosure wall and a separate portion of the enclosure of the electrical device, for example between the edge of a motor shell and an end shield attached to the shell. These grommets can not be attached to the notch in the enclosure if the end shield is already attached to the enclosure shell. It is necessary to first disassemble the end shield from the motor shell in order to access the notch provided for the grommet. Once the grommet is inserted in the notch and the electrical conductors passed through the grommet, then the end shield can be reassembled to the motor shell enclosure wall. Thus, this particular design of protective grommet requires that the grommet be positioned at an interface between two enclosure wall members and cannot be used other than at an edge of an enclosure wall.
To overcome the disadvantages of the prior art, a grommet design is needed that can be attached in an opening in an enclosure wall of an electrical device where the positioning of the opening is not limited to the interface of two wall sections of the electrical device, such as a motor shell wall and an end shield. The grommet would still provide the benefits of sealing the opening in the enclosure wall and would also provided a connection for a separate length of conduit to protect the electrical conductors extending from the electrical device.